1. Field of the Invention
The present invention relates to switching devices in a switchboard, which can communicate with one another via a databus, or can communicate with a higher-level programmable logic controller (PLC).
2. Description of the Prior Art
Systems with switching devices, including the associated control and, possibly, measurement devices, as well as control-unit and display devices, which can be coupled via bus-compatible coupling elements to a databus, for example a two-wire bus, have been disclosed in WO-94/24647. In that publication, the normal control wiring is avoided. The databus has connected to it an interface assembly, which is connected via a serial transmission bus to a communication processor of a programmable logic controller. The interface assembly has a microprocessor with a control program which, with an appropriate configuration, allows the switchboard to be operated as an independent functional island--that is to say, a closed system. Furthermore, higher-level action on the control of the switching, control and measurement devices is possible by the communication processor, which may be located remotely. This system design relieves higher-level systems, such as the programmable logic controller, of control functions, by the communication processor, the protective function is locally decoupled and thus accelerated, and it is possible for the system switchboard to have a defined behavior in the event of failure of the transmission bus.